Solar panels. Solar (photovoltaic) panels (grey) & solar thermal heating panels (black) on the roof of the Natatorium building. The solar panels cont- ain silicon, a semiconducting material which can convert sunlight directly into electricity. The thermal heating panels absorb the warmth of the Sun to heat water for a swimming pool. The Natat- orium swimming pool & its solar panels were built for the 1996 Olympic Games in Atlanta, USA. It has 2856 panels with a total area of 3175 square metres. They can generate of total of 340 kilo- watts of electricity, making it the largest photo- voltaic roof system in the world at completion.